Fuente: WIPO "rice" 1709. Rice, J. V. Jan. 22. Rock drills.-A hydrocarbon or gas actuated rock drill has a crank-shaft 7, which is mounted in soft-metal bearings 6 and carries a hub 9 to which a fly-wbeel 8 is attached. The hub has a commutator ring 11, which makes contact with a brush 12, so as to complete the circuit for the electric ignition at a point of the piston's stroke determined by a hole in the boss into which a spring-pressed pin 18 on the brush-holding ring 17 is placed. The fluid for use in the vapour flows from a pipe and needle valve through an outlet in the seat for the air valve, air being admitted on each back stroke of the piston. The explosive mixture is formed in the space in front of the cylinder, and is compressed on the forward stroke, escaping to the rear when the passage 62, which contains the valve 63, is uncovered ; it is then compressed and exploded. Burnt gas escapes from the rear of the piston through a port 65. A packing-box 22 for the piston-rod is interposed between the cylinder 20 and an extension 4 from the casing, one of the side walls of which is removable. The forward end of the piston-rod carries a yoke, in the slot of which plays a block 28 carried by the crank-pin 29. The yoke has a threaded stud 31, which carries a tube 32, playing through a bearing 33 and having an enlarged head 34. The drill-carrier 37 plays loosely in this tube and sleeve, and has a reduced portion 38 to engage balls 39, contained in a V- shaped raceway formed by two rings 41, 42 held in position against the cap 35 by a spring 43. The tool is cushioned by the spring 43, which is compressed when the rings 41, 42 are separated by the balls, and rotation is produced by providing spiral slots 44 in the tube 32. These slots engage rollers 46 carried by a ring 47, which is connected to the tool-carrier 37 by ratchet mechanism consisting of spring-pressed balls, rollers, or pins in slots. The rings 41, 42 may be held apart by a bolt 51 carried on a bell-crank lever 49 held by a tension spring 54.